1. Field of the Invention
This invention relates to a heat sink to be suitably used for applications including an apparatus for cooling integrated circuit packages, a radiating apparatus and a heat exchanger as well as to the method of producing thereof.
2. Description of the Related Art
A "pin-fin type heat sink" has so small characteristics length that the coefficient of the thermal conductivity is high, and radiate several times more heat than a "plate-fin type heat sink" having a same area of heat transfer.
A known pin-fin type heat sink normally comprises a pair of heat conductor plates 1a, 1b arranged in parallel with each other and having a plurality of paired and oppositely arranged holes 2a, 2b as typically illustrated in FIGS. 43A and 43B. A fine metal wire 3 is arranged through each pair of holes 2a, 2b and bonded at its both extremities to the inner surface of the respective holes 2a, 2b. Either one or both of the heat conductor plates 1a, 1b is in contact with a heat source or a heat transmission medium and a fluid heat exchanger or coolant (e.g., air, water, etc.) is made to flow between the two heat conductor plates 1a, 1b in a direction indicated by arrow 4 so that heat may be received by the fluid by way of the surface of the fine metal wires 3.
The fine metal wires 3 of a "pin-fin type heat sink" preferably have a very small outer diameter of less than 1 mm to maximize the coefficient of the thermal conductivity, while as many as possible fine metal wires 3 should be used in it in order to optimize the heat transfer characteristics of the heat sink. Therefore, preparation of a known pin-fin type heat sink having a configuration as described above requires a large number of processing steps including those of "boring holes" through heat conductor plates 1a, 1b and "fitting and bonding" fine metal wires 3 to the holes and consequently such a method of preparing a pin-fin type heat sink involves a high manufacturing cost.
In an attempt to bypass this problem, there has been proposed a pin-fin type heat sink that does not require a step of boring holes through heat conductor plates 1a, 1b and can be produced by simply bonding the ends of fine metal wires 3 to the inner surfaces of the heat conductor plates 1a, 1b by way of bond layers 5a, 5b of solder or silver, which are fused or brazed appropriately for bonding. While such a pin-fin type heat sink is free from the step of boring holes through heat conductor plates and therefore may be produced at a reduced cost, each fine metal wire 3 should be exactly, though temporarily, positioned on the inner surfaces of the heat conductor plates 1a, 1b when it is bonded thereto, making the pattern of arrangement of fine metal wires 3 and the distance between two adjacent wires subject to inconvenient limitations.
Besides, in areas, if any, where the fine metal wires 3 do not contact the heat conductor plates 1a, 1b, heat is conveyed from the latter to the former by way of the bond layers 5a, 5b to give rise to a very large thermal resistance or a large resistance against heat conduction in these areas.
As described above, a known heat sink having a "pin-fin type structure" not only involves rather complicated manufacturing steps and high manufacturing cost but also is subject to various limitations concerning the distance between adjacent fins and the pattern of fin arrangement, not to mention the problem of large thermal resistance.